>
> Perhaps the TT-UT correction used by Guide isn't accurate as
> far back as 6 BC?

Highly improbable that this would result in an error of hours. The
uncertainty in "delta T" for 2000 years ago is a few minutes - it's
certainly not hours!

Presumably Guide can tell you what the "delta T" value is for a given map
date. For 17th April 6BC my "SkyMap Pro" program uses a delta T value of
+9117.5 seconds - what does "Guide" use for this date?

Regards,

Chris
-----------------------------------------------------------------------
Chris Marriott, SkyMap Software, UK (chris@...)
Visit our web site at http://www.skymap.com
Astronomy software written by astronomers, for astronomers